Information terminal and battery remaining capacity calculating method

ABSTRACT

An information terminal driven by a battery disclosed herein comprises: a voltage detector configured to detect a battery voltage which is a voltage of the battery; a drive unit configured to be driven upon receiving a supply of a power source from the battery; a load calculator configured to calculate a load on the battery of the drive unit; and a battery remaining capacity calculator configured to calculate a battery remaining capacity based on the battery voltage, the battery remaining capacity calculator calculating the battery remaining capacity corrected based on the load calculated by the load calculator.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of application Ser. No.11/093,020 which claims benefit of priority under 35 U.S.C. § 119 toJapanese Patent Application No. 2004-98569, filed on Mar. 30, 2004,Japanese Patent Application No. 2004-195677, filed on Jul. 1, 2004 andJapanese Patent Application No. 2005-24089, filed on Jan. 31, 2005. Theentire contents of which are incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an information terminal and a batteryremaining capacity calculating method.

2. Related Background Art

Examples of a small-sized information terminal using a battery are adigital camera, a portable moving image reproducing apparatus, aportable sill image reproducing apparatus, and so on. Recently, a unitsuch as a hard disk drive which exerts a large influence on load changeis mounted in such a small-sized information terminal, and hence theload on the battery changes greatly according to the driving state ofthe unit.

It is very important to users to precisely display a battery remainingcapacity as means for guessing how much more time the informationterminal can be used. Methods of detecting a battery remaining capacityare a method of measuring charging/discharging currents (See JapanesePatent Application Laid-open No. Hei 5-66251, Japanese PatentApplication Laid-open No. Hei 7-260839, for example) and a method ofmeasuring a battery voltage (See Japanese Patent Application Laid-openNo. Hei 6-51876, Japanese Patent Application Laid-open No. Hei 11-55372,for example).

However, the method of measuring the charging/discharging currentsrequires a current measurer, a storage to store data on a measuredcurrent, and a CPU to calculate a battery remaining capacity from thedata, which hinders size reduction and cost reduction. Hence, it is notsuitable for the small-sized information terminal.

On the other hand, in the method of measuring the battery voltage,because of a battery characteristic, the external voltage changesaccording to internal impedance when the load changes. Therefore, in theinformation terminal with a built-in unit having large load change, aprecise battery remaining capacity cannot be detected. For example, thefollowing situation occurs: When the information terminal is powered on,the load increases, and thereby the battery remaining capacity isdisplayed at a low value, and when the information terminal isstabilized thereafter, the load decreases, and thereby the batteryremaining capacity increases. Such a change in the display of thebattery remaining capacity is confusing and very inconvenient to theusers.

A method of correcting the influence of load change is a method ofmeasuring a current flowing through a load and correcting it asdisclosed in Japanese Patent Application Laid-open No. Hei 5-66251.However, additional components such as a current detector and acomparison voltage corrector become necessary, which causes costincrease. Moreover, the information terminal, for which size reductionis indispensable, needs to avoid the addition of new components for thepurpose of detecting the battery remaining capacity as much as possible.Further, the insertion of a resistance for detecting the current into apower supply line causes a drop in voltage and wasteful powerconsumption, and hence it is not suitable for the information terminalwhich requires the longest possible time driven by the battery.

Furthermore, the hard disk drive is accessed regularly at certain timeintervals while the information terminal is reproducing moving images orsound or playing a slide show, and hence the load on the battery changesgreatly at the certain time intervals. Namely, the load while the harddisk drive is being accessed and the load while the hard disk drive isnot accessed are very different, and along with this, the load currentalso changes. Therefore, there is a problem that the battery remainingcapacity is difficult to display precisely while the informationterminal is reproducing and playing the slide show or the like.

SUMMARY OF THE INVENTION

Hence, the present invention is made in view of the aforementionedproblems, and an object of the present invention is to reduce the sizeof an information terminal while the display of a battery remainingcapacity after the influence of load change is corrected is enabled.Another object of the present invention is to be able to calculate thebattery remaining capacity as precisely as possible by calculating thebattery remaining capacity excluding a period of time when a hard diskdrive is accessed.

In order to accomplish the aforementioned and other objects, accordingto one aspect of the present invention, an information terminal drivenby a battery, comprises:

a voltage detector configured to detect a battery voltage which is avoltage of the battery;

a drive unit configured to be driven upon receiving a supply of a powersource from the battery;

a load calculator configured to calculate a load on the battery of thedrive unit; and

a battery remaining capacity calculator configured to calculate abattery remaining capacity based on the battery voltage, the batteryremaining capacity calculator calculating the battery remaining capacitycorrected based on the load calculated by the load calculator.

According to another aspect of the present invention, a batteryremaining capacity calculating method in an information terminal drivenby a battery, comprises the steps of:

detecting a battery voltage which is a voltage of the battery;

calculating a load on the battery of a drive unit which is driven uponreceiving a supply of a power source from the battery; and

in calculating a battery remaining capacity based on the batteryvoltage, calculating the battery remaining capacity corrected based onthe calculated load.

According to another aspect of the present invention, a recording mediumhas a program for causing an information terminal driven by a battery tocalculate a battery remaining capacity recorded thereon, and the programcauses the information terminal to execute process comprising the stepsof:

detecting a battery voltage which is a voltage of the battery;

calculating a load on the battery of a drive unit which is driven uponreceiving a supply of a power source from the battery; and

in calculating a battery remaining capacity based on the batteryvoltage, calculating the battery remaining capacity corrected based onthe calculated load.

According to another aspect of the present invention, an informationterminal driven by a battery, comprises:

a data storage configured to be driven upon receiving a supply of apower source from the battery, data being stored in the data storage;

a voltage detector configured to detect a battery voltage which is avoltage of the battery;

a battery remaining capacity calculator configured to calculate abattery remaining capacity based on the battery voltage, the batteryremaining capacity calculator calculating the battery remaining capacityafter access to the data storage is completed.

According to another aspect of the present invention, an informationterminal driven by a battery, comprises:

a data storage configured to be driven upon receiving a supply of apower source from the battery and store data;

a data storage load calculator configured to calculate a load of thedata storage;

a voltage detector configured to detect a battery voltage which is avoltage of the battery; and

a battery remaining capacity calculator configured to calculate abattery remaining capacity based on the battery voltage, the batteryremaining capacity calculator calculating the battery remaining capacitywhen the load of the data storage calculated by the data storage loadcalculator is lower than a given value.

According to another aspect of the present invention, a batteryremaining capacity calculating method in an information terminal drivenby a battery, comprises the steps of:

judging whether access to a data storage is completed, the data storagebeing driven upon receiving a supply of a power source from the battery;and

calculating a battery remaining capacity based on a battery voltagewhich is a voltage of the battery after the access to the data storageis completed.

According to another aspect of the present invention, a batteryremaining capacity calculating method in an information terminal drivenby a battery, comprises the steps of:

calculating a load of a data storage which is driven upon receiving asupply of a power source from the battery; and

calculating a battery remaining capacity based on a battery voltagewhich is a voltage of the battery when the calculated load is lower thana given value.

According to another aspect of the present invention, a recording mediumhas a program for causing an information terminal driven by a battery tocalculate a battery remaining capacity recorded thereon, and the programcauses the information terminal to execute process comprising the stepsof:

judging whether access to a data storage is completed, the data storagebeing driven upon receiving a supply of a power source from the battery;and

calculating a battery remaining capacity based on a battery voltagewhich is a voltage of the battery after the access to the data storageis completed.

According to another aspect of the present invention, a recording mediumhas a program for causing an information terminal driven by a battery tocalculate a battery remaining capacity recorded thereon, wherein theprogram causes the information terminal to execute process comprisingthe steps of:

calculating a load of a data storage which is driven upon receiving asupply of a power source from the battery; and

calculating a battery remaining capacity based on a battery voltagewhich is a voltage of the battery when the calculated load is lower thana given value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an example of the configuration of aninformation terminal according to a first embodiment;

FIG. 2 is a graph showing a relation between a battery voltage and abattery remaining capacity;

FIG. 3 is a flowchart explaining the contents of battery remainingcapacity calculation processing according to the first embodiment andthe contents of a part of battery remaining capacity calculationprocessing according to a second embodiment;

FIG. 4 is a diagram showing an example of a 5° C. voltage-remainingcapacity conversion table included in the information terminal accordingto the first embodiment and the second embodiment;

FIG. 5 is a diagram showing an example of a 15° C. voltage-remainingcapacity conversion table included in the information terminal accordingto the first embodiment and the second embodiment;

FIG. 6 is a diagram showing an example of a 25° C. voltage-remainingcapacity conversion table included in the information terminal accordingto the first embodiment and the second embodiment;

FIG. 7 is a diagram showing an example of a 45° C. voltage-remainingcapacity conversion table included in the information terminal accordingto the first embodiment and the second embodiment;

FIG. 8 is a diagram showing an example of a 20° C. voltage-remainingcapacity conversion table generated from the 15° C. voltage-remainingcapacity conversion table shown in FIG. 5 and the 25° C.voltage-remaining capacity conversion table shown in FIG. 6;

FIG. 9 is a diagram showing an example of a 1000 mA voltage-remainingcapacity conversion table generated from the 20° C. voltage-remainingcapacity conversion table shown in FIG. 8;

FIG. 10 is a diagram showing a table representing a relation between anoperating state of a hard disk drive and its current consumption in theinformation terminal according to the second embodiment;

FIG. 11 is a diagram showing an example of the transition of theoperating state of the hard disk drive and its current consumption inthe information terminal according to the second embodiment;

FIG. 12 is a diagram showing an example of the transition of theoperating state of the hard disk drive in the information terminalaccording to the second embodiment;

FIG. 13 is a diagram showing an example of the transition of theoperating state of the hard disk drive in the information terminalaccording to the second embodiment;

FIG. 14 is a block diagram showing an example of the configuration ofthe information terminal according to the second embodiment;

FIG. 15 is a flowchart explaining the contents of hard disk drive loadcount processing according to the second embodiment;

FIG. 16 is a flowchart explaining the contents of a part of the batteryremaining capacity calculation processing according to the secondembodiment;

FIG. 17 is a graph showing a relation between an elapsed time and abattery remaining capacity in a case where a correction is madeaccording to the operating state of the hard disk drive and a case whereno correction is made;

FIG. 18 is a diagram showing an example of calculation of a constantload according to the processing contents of the information terminal;

FIG. 19 is a diagram showing an example of a graph of a relation betweena load current and a time when the information terminal is playing aslide show;

FIG. 20 is a flowchart explaining the contents of a battery remainingcapacity calculation processing according to a third embodiment and thecontents of a part of battery remaining capacity calculation processingaccording to a fourth embodiment (First part);

FIG. 21 is the flowchart explaining the contents of the batteryremaining capacity calculation processing according to the thirdembodiment and the contents of a part of the battery remaining capacitycalculation processing according to the fourth embodiment (Second part);

FIG. 22 is a flowchart explaining the contents of hard disk drive loadcount processing according to the fourth embodiment and a sixthembodiment;

FIG. 23 is a flowchart explaining the contents of a part of the batteryremaining capacity calculation processing according to the fourthembodiment;

FIG. 24 is a flowchart explaining the contents of battery remainingcapacity calculation processing according to a fifth embodiment;

FIG. 25 is a flowchart explaining the contents of battery remainingcapacity calculation processing according to the sixth embodiment; and

FIG. 26 is a diagram showing an example of a configuration when thebattery remaining capacity calculation processing is realized byhardware.

DETAILED DESCRIPTION OF THE EMBODIMENTS First Embodiment

In this embodiment, in a small-sized information terminal with abuilt-in unit having large load change, it is possible to, incalculating a battery remaining capacity, correct the influence of theload change and acquire a battery remaining capacity with highprecision. Further details will be given below.

FIG. 1 is a block diagram showing an example of the internalconfiguration of the information terminal according to this embodiment.As shown in FIG. 1, the information terminal includes a CPU 10, an LCDbacklight 12, a hard disk drive 14, a display 18, and loads 16 otherthan these. This information terminal has a built-in battery 20, and apower source supplied from the battery 20 is supplied to the CPU 10, theLCD backlight 12, the hard disk drive 14, the display 18, and the otherloads 16 via a DC/DC converter 22. Namely, a voltage stabilized ortransformed by the DC/DC converter 22 is supplied to a drive being aload thereof. The CPU 10 includes therein an AD converter 30, a RAM 32,and a ROM 34. This CPU 10 composes a central processing unit in thisembodiment.

This information terminal also includes a voltage detecting circuit 40.This voltage detecting circuit detects a voltage between the battery 20and the DC/DC converter 22, and a detected value is supplied as abattery voltage to the AD converter 30 of the CPU 10. This detectedvalued is converted into digital data and incorporated into the CPU 10.

The battery 20 has a built-in temperature detecting circuit 42. Thistemperature detecting circuit 42 is, for example, composed of athermistor, and an output of an analog signal from the temperaturedetecting circuit 42 is inputted to the AD converter 30 and incorporatedas digital data into the CPU 10.

Next, the principle of battery remaining capacity calculation accordingto this embodiment will be described based on FIG. 2. FIG. 2 is a graphshowing a relation between a battery voltage and a battery remainingcapacity when the load is high (1200 mA, for example) and when the loadis low (400 mA, for example). As can be seen from this graph, even ifmeasured battery voltages have the same value, actual battery remainingcapacities differ when the load is high and when the load is low. Hence,in this embodiment, relations between the battery voltage and thebattery remaining capacity with respect to some representative loadvalues are previously prepared by tables. In finding a battery remainingcapacity, a load of the information terminal concerned is calculated,and by performing a correction according to the load when the batteryremaining capacity is found based on a measured battery voltage, themore precise battery remaining capacity can be calculated.

FIG. 3 is a flowchart explaining the contents of battery remainingcapacity calculation processing according to this embodiment. Thisbattery remaining capacity calculation processing shown in FIG. 3 isrealized by making the CPU 10 read and execute a battery remainingcapacity calculation processing program stored in the ROM 34.

As shown in FIG. 3, the information terminal acquires a battery voltagewhich is a voltage of the battery 20 (step S10). Namely, the voltage ofthe battery 20 detected by the voltage detecting circuit 40 is acquiredas digital data via the AD converter 30.

Then, the information terminal acquires a battery temperature which is atemperature of the battery 20 (step S12). Namely, the batterytemperature as analog data detected by the temperature detecting circuit42 provided in the battery 20 is acquired as digital data via the ADconverter 30.

Thereafter, the information terminal acquires a constant load (stepS14). This constant load changes according to the operation mode of theCPU 10. In this embodiment, it is assumed that the CPU 10 has threeoperation modes: low-speed, medium-speed, and high-speed operationmodes. The CPU 10 keeps track of in which mode out of these threeoperation modes the CPU 10 is at the moment. In this embodiment, theconstant load is 400 mA in the low-speed mode, the constant load is 500mA in the medium-speed mode, and the constant load is 600 mA in thehigh-speed mode.

Subsequently, the information terminal acquires a hard disk driveoperating rate (step S16). In this embodiment, the hard disk drive 14outputs an access signal which indicates whether it is accessed or notto the CPU 10. Therefore, the CPU 10 can acquire this access signal andcalculate a ratio between a period of time when the hard disk drive 14is accessed and a period of time when it is not accessed at any time. Inthis embodiment, this access period ratio is defined as the hard diskdrive operating rate.

Then, the information terminal acquires an LCD backlight luminancecoefficient (step S18). In this embodiment, the CPU 10 outputs aluminance signal which controls the luminance of the LCD backlight 12 tothe LCD backlight 12. Hence, the CPU 10 can keep track of a luminancecoefficient of the LCD backlight 12 based on this luminance. In thisembodiment, the LCD backlight luminance coefficient can be set between0% and 100% in steps of 10%.

Thereafter, the information terminal calculates a load (step S20). Inthis embodiment, the load is found by the following expression (1).load=constant load+hard disk drive access load×hard disk drive operatingrate+LCD load×LCD backlight luminance coefficient   (1)

In this embodiment, it is assumed that the hard disk drive access loadis, for example, 500 mA, and the LCD load is, for example, 100 mA. Bysubstituting the constant load acquired in step S14, the hard disk driveoperating rate acquired in step S16, and the LCD backlight luminancecoefficient acquired in step S18 into this expression, a current loadcan be calculated.

Subsequently, the information terminal generates a voltage-remainingcapacity conversion table which corresponds to the battery temperature(step S22). In this embodiment, four kinds of voltage-remaining capacityconversion tables according to temperature are stored in ROM 34 in theCPU 10. FIG. 4 to FIG. 7 are diagrams showing an example of these fourkinds of voltage-remaining capacity conversion tables TB10 to TB40according to temperature. FIG. 4 is a diagram showing thevoltage-remaining capacity conversion table TB10 when the batterytemperature is 5° C., FIG. 5 is a diagram showing the voltage-remainingcapacity conversion table TB20 when the battery temperature is 15° C.,FIG. 6 is a diagram showing the voltage-remaining capacity conversiontable TB30 when the battery temperature is 25° C., and FIG. 7 is adiagram showing the voltage-remaining capacity conversion table TB40when the battery temperature is 45° C.

As can be seen from these figures, in this embodiment, the relationbetween the remaining capacity and the battery voltage is tabulated withthree loads of 400 mA, 800 mA, and 1200 mA as representative values.Using these voltage-remaining capacity conversion tables, avoltage-remaining capacity conversion table at the battery temperatureacquired in step S12 is generated by line interpolation.

For example, it is assumed that the battery temperature acquired in stepS12 is 20° C. In this case, by linearly interpolating voltage values inthe 15° C. voltage-remaining capacity conversion table TB20 shown inFIG. 5 and voltage values in the 25° C. voltage-remaining capacityconversion table TB30 shown in FIG. 6, voltage values in a 20° C.voltage-remaining capacity conversion table are generated. Morespecifically, a voltage Y after correction can be calculated by thefollowing expression (2) $\begin{matrix}{Y = {{{\frac{\left( {{Y\quad 2} - {Y\quad 1}} \right)}{\left( {{T\quad 2} - {T\quad 1}} \right)}\left( {T - {T\quad 1}} \right)} + {Y\quad 1\quad{where}\quad T\quad 1}} < {T\quad 2}}} & (2)\end{matrix}$where T1 (15° C.) is the temperature of the low-temperature sidevoltage-remaining capacity conversion table, T2 (25° C.) is thetemperature of the high-temperature side voltage-remaining capacityconversion table, T (20° C.) is the battery temperature, Y1 is a voltagevalue at T1, and Y2 is a voltage value at T2.

Consequently, the voltage-remaining capacity conversion table TB50 whenthe calculated battery temperature is 20° C. is as shown in FIG. 8. Thisvoltage-remaining capacity conversion table TB50 is stored in the RAM 32of the CPU 10.

Incidentally, in this embodiment, by using the 5° C. and 15° C.voltage-remaining capacity conversion tables when the batterytemperature is lower than 5° C. and using the 25° C. and 45° C.voltage-remaining capacity conversion tables when the batterytemperature is higher than 45° C., and substituting corresponding valuesinto the expression (2), voltage-remaining capacity conversion tables atthese temperatures can be obtained.

Then, as shown in FIG. 3, the information terminal generates avoltage-remaining capacity conversion table corresponding to the loadcalculated in step S20 (step S24). Namely, based on thevoltage-remaining capacity conversion table generated in step S22, thevoltage-remaining capacity conversion table corresponding to the loadcalculated in step S20 is generated and stored in the RAM 32.

For example, it is assumed that the load calculated in step S20 is 1000mA. In this case, by linearly interpolating voltage values at 800 mA andvoltage values at 1200 mA in the voltage-remaining capacity conversiontable TB50 shown in FIG. 8, voltage values in a 1000 mAvoltage-remaining capacity conversion table TB60 are generated. Morespecifically, a voltage Y after correction can be calculated by thefollowing expression (3) $\begin{matrix}{Y = {{{\frac{\left( {{Y\quad 2} - {Y\quad 1}} \right)}{\left( {{L\quad 2} - {L\quad 1}} \right)}\left( {L - {L\quad 1}} \right)} + {Y\quad 1\quad{where}\quad L\quad 1}} < {L\quad 2}}} & (3)\end{matrix}$where L1 (800 mA) is a low-load side current value, L2 (1200 mA) is ahigh-load side current value, L is the load calculated in step S20, Y1is a voltage value at L1, and Y2 is a voltage value at L2.

Consequently, the voltage-remaining capacity conversion table TB60 whenthe calculated load is 1000 mA is as shown in FIG. 9.

Thereafter, as shown in FIG. 3, the information terminal calculates abattery remaining capacity based on the voltage-remaining capacityconversion table TB60 after the load is corrected and the temperature iscorrected (step S26). Namely, by linearly interpolating numerical valuesin the voltage-remaining capacity conversion table TB60 stored in theRAM 32, a battery remaining capacity corresponding to the batteryvoltage acquired in step S10 is calculated.

For example, it is assumed that the battery voltage acquired in step S10is 3.55 V In this case, by linearly interpolating 3.54 V (batteryremaining capacity of 40%) and 3.60 V (battery remaining capacity of50%) in the voltage-remaining capacity conversion table TB60 shown inFIG. 9, the battery remaining capacity when the battery voltage is 3.55V is calculated. More specifically, a battery remaining capacity X aftercorrection can be calculated by the following expression (4)$\begin{matrix}{Y = {{{\frac{\left( {{X\quad 2} - {X\quad 1}} \right)}{\left( {{Y\quad 2} - {Y\quad 1}} \right)}\left( {Y\quad - {Y\quad 1}} \right)} + {X\quad 1\quad{where}\quad Y\quad 1}} < {Y\quad 2}}} & (4)\end{matrix}$where Y1 (3.54 V) is a low-voltage side voltage value, Y2 (3.60 V) is ahigh-voltage side voltage value, Y is the voltage acquired in step S10,X1 is a battery remaining capacity at Y1, and X2 is a battery remainingcapacity at Y2.

Consequently, the result of calculation of the battery remainingcapacity is approximately 42%. In this embodiment, this calculatedbattery remaining capacity is temporarily stored in the RAM 32.

Thereafter, as shown in FIG. 3, the information terminal reads thecalculated battery remaining capacity from the RAM 32 and displays it onthe display 18 (step S28). Various methods of displaying the batteryremaining capacity are thought out. For example, with a screen of theinformation terminal as the display 18, 42% may be displayednumerically, or with a bar-form liquid crystal display as the display18, a bar of this liquid crystal display may have a length correspondingto 42%.

As described above, according to this embodiment, the operating rate ofa unit (for example, the hard disk drive 14, the LCD backlight 12, theoperation mode of the CPU 10, or the like) which greatly contributes toload change is calculated by measuring a signal which the unit outputsor a signal which the unit receives, and by making a correction based onthe calculated result, the battery remaining capacity is displayed withhigh precision. Moreover, the correction is made using the CPU 10 whichis originally built in the information terminal, whereby the addition ofa new unit is not necessary, which can realize size reduction and costreduction of the information terminal.

Further, the battery temperature of the battery 20 is detected using thetemperature detecting circuit 42, the correction is further made basedon this battery temperature, and consequently the battery remainingcapacity can be displayed with higher precision.

Second Embodiment

In the aforementioned first embodiment, by calculating the hard diskdrive operating rate based on the access signal of the hard disk drive14, the load of the hard disk drive 14 is calculated, but in the secondembodiment, by specifying the state of the hard disk drive 14 moreprecisely, the load of the hard disk drive 14 is found more precisely.

More specifically, the hard disk drive 14 in this embodiment has fiveoperating states as shown in FIG. 10 and FIG. 11. Namely, it has anaccess state (hereinafter called an AC load) where the hard disk drive14 is actually being accessed, a performance idle state (hereinaftercalled a PI load) for 300 ms after the completion of the access, anactive idle state (hereinafter called an AI load) for 10 seconds afterthe completion of the performance idle state, a low power idle state(hereinafter called a LPI load) after the completion of the active idlestate, and a standby state (hereinafter called an ST load) to which thehard disk drive 10 shifts based on an instruction from the CPU 10 as itsoperating states.

In this embodiment, the current consumption in the access state is 600mA, the current consumption in the performance idle state is 400 mA, thecurrent consumption in the active idle state is 190 mA, the currentconsumption in the low power idle state is 170 mA, and the currentconsumption in the standby state is 40 mA. Incidentally, in thisembodiment, the state of the hard disk drive 14 is sampled 32 times persecond. In other words, the operating state of the hard disk drive 14 isspecified in a sampling cycle of 31.25 ms.

Moreover, the access signal in the first embodiment goes low when thehard disk drive 14 is in the access state, and goes high when it is notin the access state.

Accordingly, in this embodiment, even when the access signal indicatesthe state where the hard disk drive 14 is not accessed, the currentconsumption differs greatly according to whether the hard disk drive 14is in the performance idle state, the active idle state, the low poweridle state, or the standby state. Hence, the precise load of the harddisk drive 14 cannot be calculated by only detecting a low level and ahigh level of the access signal and counting them.

This is obvious, for example, if a case where the hard disk drive 14shifts in order of the access state, the performance idle state, theaccess state, the performance idle state, the access state, and theperformance idle state as shown in FIG. 12 and a case where the harddisk drive 14 shifts in order of the access state, the performance idlestate, the active idle state, and the access state as shown in FIG. 13are compared.

In FIG. 12 and FIG. 13, the numbers of low-level access signals (thatis, access states) counted per second are the same, that is, six.However, the load of the hard disk drive 14 is 438 mA in the case ofFIG. 12 and 333 mA in the case of FIG. 13, and the difference betweenthem is as large as 105 mA. This value exists as a latent error when theload of the hard disk drive 14 is calculated based on only the accesssignal indicating whether the hard disk drive 14 is accessed or not.

Hence, in this embodiment, the load of the hard disk drive 14 iscalculated using the following expression (5). $\begin{matrix}{{{load}\quad{of}\quad{hard}\quad{disk}\quad{drive}} = {{{AC}\quad{load} \times \quad\left( {{N\_ ON}/32} \right)} + {{PI}\quad{load} \times \left( {{N\_ OFF}{{\_ PI}/32}} \right)} + {{AI}\quad{load} \times \left( {{N\_ OFF}{{\_ AI}/32}} \right)} + {{LPI}\quad{load} \times \left( {{N\_ OFF}{{\_ LPI}/32}} \right)} + {{ST}\quad{load} \times \left( {N = {{OFF\_ ST}/32}} \right)}}} & (5)\end{matrix}$

Namely, since 32 samplings per second are performed, the currentconsumption per second of the hard disk drive 14 is calculated based onstates obtained by the samplings. Here, a counter N_ON is the number ofaccess states of the hard disk drive 14 counted during immediatelypreceding one second, a counter N_OFF_PI is the number of performanceidle states of the hard disk drive 14 counted during the immediatelypreceding one second, a counter N_OFF_AI is the number of active idlestates of the hard disk drive 14 counted during the immediatelypreceding one second, a counter N_OFF_LPI is the number of low poweridle states of the hard disk drive 14 counted during the immediatelypreceding one second, and a counter N_OFF_ST is the number of standbystates of the hard disk drive 14 counted during the immediatelypreceding one second. Namely, the counters N_ON, N_OFF_PI, N_OFF_AI,N_OFF_LPI, and N_OFF_ST are variables which are cleared to zero everyone second.

Incidentally, as concerns the standby state (ST load), the hard diskdrive 14 is shifted thereto by an instruction from the CPU 10 to thehard disk drive 14, so that the CPU 10 itself can specify this standbystate.

Moreover, a load of the entire information terminal is calculated by anexpression (6) in place of the expression (1) in the first embodiment.load=constant load+load of hard disk drive+LCD load×LCD backlightluminance coefficient   (6)

FIG. 14 is a block diagram showing an example of the internalconfiguration of an information terminal according to this embodiment.As can be seen from FIG. 14, the internal configuration of theinformation terminal according to this embodiment is schematically thesame as that in the aforementioned first embodiment, but different inthat a command signal which causes the hard disk drive 14 to shift tothe standby state is outputted from the CPU 10 to the hard disk drive14. Namely, in this embodiment, the CPU 10 positively causes the harddisk drive 14 to shift to the standby state, and thereby the commandsignal is outputted from the CPU 10 to the hard disk drive 14. Normally,the command signal which causes the hard disk drive 14 to shift to thestandby state is outputted when the hard disk drive 14 is in the lowpower idle state. The other configuration is the same as that in theaforementioned first embodiment.

Next, hard disk drive load count processing in this embodiment will beexplained. FIG. 15 is a flowchart explaining the contents of the harddisk drive load count processing according to this embodiment. The harddisk drive load count processing shown in FIG. 15 is realized by makingthe CPU 10 read and execute a hard disk drive load count processingprogram stored in the ROM 34. This hard disk drive load count processingis started every 31.25 ms to make a count as described above.

As shown in FIG. 15, the information terminal judges whether the harddisk drive 14 is in the active state (step S100). More specifically, theinformation terminal judges whether the access signal of the hard diskdrive 14 indicates the access state. When the hard disk drive 14 is inthe active state (step S100: Yes), the counter N_ON is incremented byone (step S102).

On the other hand, when the hard disk drive 14 is not in the activestate (step S100: No), it is judged whether the hard disk drive 14 is inthe standby state (step S104). More specifically, since the CPU 10outputs the command signal to shift the hard disk drive 14 to thestandby state to the hard disk drive 14, the CPU 10 can keep track ofwhether the hard disk drive 14 is in the standby state. Therefore, theCPU 10 itself judges whether it has brought the hard disk drive into thestandby state. When the hard disk drive 14 is in the standby state (stepS104: Yes), the counter N_OFF_ST is incremented by one (step S106).

On the other hand, when it is judged that the hard disk drive 14 is notin the standby state (step S104: No), it is judged whether the accesssignal is in a non-access state continuously in more than 10 times ofsamplings (step S108). More specifically, the CPU 10 performs processingin which when the CPU 10 starts counting the number of continuousnon-accesses from zero immediately after the access signal shifts fromthe access state (low level) to the non-access state (access level) andthe non-access state is continued at the time of sampling, the number ofcontinuous non-accesses is incremented by one.

Then, the CPU 10 judges whether the number of continuous non-accesses ismore than 10. As described above, in this embodiment, the performanceidle state is set to continue for 300 ms if there is no access.Therefore, in this embodiment in which sampling is performed every 31.25ms, the period of time of the performance idle state corresponds to theperiod of time of 10 samplings, so that when the number of times theaccess signal indicating the non-access state is continuously sampled is10 or less, the hard disk drive 14 can be judged to be in theperformance idle state.

When the number of continuous non-accesses is 10 or less (step S108:No), the counter N_OFF_PI is incremented by one (step S110).

On the other hand, when the number of continuous non-accesses is morethan 10 (step S108: Yes), it is judged whether the number of continuousnon-accesses is more than 10+320=330 (step S112). More specifically, theCPU 10 judges whether the number of continuous non-accesses is more than330. As described above, in this embodiment, the performance idle stateis set to continue for 300 ms, and the active idle state is set tocontinue for 10 seconds thereafter. Therefore, in this embodiment inwhich sampling is performed every 31.25 ms, the period of time of theperformance idle state corresponds to the period of time of 10 samplingsand the period of the active idle state corresponds to the period oftime of 320 samplings, so that when the number of continuousnon-accesses which indicates the number of times the non-access state iscontinuously sampled is more than 10 and 330 or less, the hard diskdrive 14 can be judged to be in the active idle state. When the numberof continuous non-accesses is 330 or less (step S112: No), the counterN_OFF_AI is incremented by one (step S114).

On the other hand, when the number of continuous non-accesses is morethan 330 (step S112: Yes), the counter N_OFF_LPI is incremented by one(step S116).

By the aforementioned processing in step S102, step S106, step S110,step S114, or step S116, the hard disk drive load count processing isended.

Next, battery remaining capacity calculation processing in thisembodiment will be explained. FIG. 16 is a flowchart explaining thecontents of the battery remaining capacity calculation processingaccording to this embodiment. This battery remaining capacitycalculation processing shown in FIG. 16 is realized by making the CPU 10read and execute a battery remaining capacity calculation processingprogram stored in the ROM 34. In this embodiment, this battery remainingcapacity calculation processing is started once per second.

As shown in FIG. 16, the information terminal acquires a battery voltagewhich is a voltage of the battery 20 (step S110). Namely, the voltage ofthe battery 20 detected by the voltage detecting circuit 40 is acquiredas digital data via the AD converter 30.

Then, the information terminal acquires a battery temperature which is atemperature of the battery 20 (step S12). Namely, the batterytemperature as analog data detected by the temperature detecting circuit42 provided in the battery 20 is acquired as digital data via the ADconverter 30.

Thereafter, the information terminal acquires a constant load (stepS14).

This constant load changes according to the operation mode of the CPU10. In this embodiment, it is assumed that the CPU 10 has threeoperation modes: low-speed, medium-speed, and high-speed operationmodes. The CPU 10 keeps track of in which mode out of these threeoperation modes the CPU 10 is at the moment. In this embodiment, theconstant load is 400 mA in the low-speed mode, the constant load is 500mA in the medium-speed mode, and the constant load is 600 mA at thehigh-speed mode.

Subsequently, the information terminal acquires a load of the hard diskdrive 14 (step S200). In this embodiment, the load of the hard diskdrive 14 is calculated based on the aforementioned expression (5).Namely, the load of the hard disk drive 14 is calculated based on theresult of samplings of the state of the hard disk drive 14 during theimmediately preceding one second by the hard disk drive load countprocessing. More specifically, by substituting the count number of N_ON,the count number of N_OFF PI, the count number of N_OFF_AI, the countnumber of N_OFF_LPI, and the count number of N_OFF_ST into theexpression (5), the current load of the hard disk drive 14 can becalculated.

Then, these counters N_ON, N_OFF_PI, N_OFF_AI, N_OFF_LPI, and N_OFF_STare cleared and set to zero (step S202).

Thereafter, the information terminal acquires an LCD backlight luminancecoefficient (step S18). In this embodiment, the CPU 10 outputs aluminance signal which controls the luminance of the LCD backlight 12 tothe LCD backlight 12. Hence, the CPU 10 can keep track of a luminancecoefficient of the LCD backlight 12 based on this luminance. In thisembodiment, the LCD backlight luminance coefficient can be set between0% and 100% in steps of 10%.

Subsequently, the information terminal calculates a whole load (stepS20). In this embodiment, the whole load is calculated based on theaforementioned expression (6). The processing after this is the same asthat in the aforementioned first embodiment, and hence the explanationthereof is omitted. Moreover, the voltage-remaining capacity conversiontables TB10 to TB40 according to temperature included in the informationterminal of this embodiment are the same as those in FIG. 4 to FIG. 7 inthe aforementioned first embodiment, and hence the explanation thereofis omitted.

As described above, according to this embodiment, the load of the harddisk drive 14 is calculated with higher precision based on the operatingstates of the hard disk drive 14. Consequently, the battery remainingcapacity can be displayed with higher precision.

FIG. 17 is a graph showing a relation between an elapsed time and abattery remaining capacity when a case where a correction is madeaccording to the operating states of the hard disk drive 14 (thisembodiment) and a case where no correction is made are compared. In FIG.17, the case where no correction is made according to the operatingstates of the hard disk drive 14 means a case where in all states wherethe hard disk drive 14 is not in the access state, all calculations aremade using the current consumption in the performance idle state.

As can be seen from FIG. 17, when the access rate of the hard disk drive14 is 100% of the total, the precision remains unchanged regardless ofthe presence or absence of a correction. However, when the access rateof the hard disk drive 14 is 6% of the total, it is known that the loadof the hard disk drive 14 is estimated larger than the actual one if nocorrection is made, so that a distance from an ideal line becomes largerand thereby the precision drops greatly.

Third Embodiment

First, a basic concept of a battery remaining capacity calculatingmethod according to this embodiment will be described based on FIG. 19.FIG. 19 is a diagram showing an example of a graph of a relation betweena load current and a time when an information terminal according to thisembodiment is playing a slide show.

As can be seen from FIG. 19, the load current increases regularly atcertain time intervals while the information terminal is playing theslide show. This is because the hard disk drive is accessed regularly atthe certain time intervals while the slide show is being played. In theexample in FIG. 19, the hard disk drive is accessed in a cycle of about30 seconds to about 40 seconds.

Since the load current increases while the hard disk drive is accessedalthough it is a short time, the battery voltage also drops sharply.Hence, even if a battery voltage is acquired while the hard disk driveis accessed, this battery voltage is not regarded as the voltage whichcorrectly reflects the battery remaining capacity. Accordingly, in thisembodiment, when the information terminal is executing processing suchas the slide show in which the hard disk drive is accessed at certaintime intervals, the battery voltage is measured after the access to thehard disk drive is completed and then the battery remaining capacity iscalculated. A detailed explanation of the battery remaining capacitycalculating method in the information terminal according to thisembodiment will be given below.

Incidentally, the internal configuration of the information terminalaccording to this embodiment is the same as that in FIG. 1 in theaforementioned first embodiment.

FIG. 20 and FIG. 21 are flowcharts explaining the contents of batteryremaining capacity calculation processing according to this embodiment.The battery remaining capacity calculation processing shown in FIG. 20and FIG. 21 is realized by making the CPU 10 read and execute a batteryremaining capacity calculation processing program stored in the ROM 34.In this embodiment, this battery remaining capacity calculationprocessing is executed every 31.25 ms (32 times per second).

As shown in FIG. 20, it is first judged whether the information terminalis in the middle of moving image reproduction, sound reproduction, orslide show play (step S1010). Here, the moving image reproduction, soundreproduction, and slide show play are examples of the processing inwhich the hard disk drive is accessed at certain time intervals, and theprocessing in which the hard disk drive is accessed at the certain timeintervals is not limited to the above.

When it is judged that the information terminal is in the middle ofmoving image reproduction, sound reproduction, or slide show play (stepS1010: YES), it is judged whether the access signal outputted from thehard disk drive 14 to the CPU 10 indicates that the hard disk drive 14is not being accessed (step S1020). When the access signal indicatesthat the hard disk drive is being accessed (step S1020: NO), a counterACCESS_OFF is cleared and returned to zero (step S1030). Then, theprocessing returns to step S1020.

On the other hand, when the access signal indicates that the hard diskdrive is not being accessed (step S1020: YES). the counter ACCESS_OFF isincremented by one (step S1040).

Then, the information terminal judges whether the counter ACCESS_OFF is32 or more (step S1050). As described above, this battery remainingcapacity calculation processing is executed 32 times per second, wherebythe case where the counter ACCESS_OFF is 32 or more means that onesecond or more has passed since the access to the hard disk drive 14 wascompleted.

When the counter ACCESS_OFF is not 32 or more (step S1050: NO), theprocessing returns to step S1020 described above.

On the other hand, when the counter ACCES_OFF is 32 or more (step S1050:YES) or it is judged that the information terminal is neither in themiddle of moving image reproduction, in the middle of soundreproduction, nor in the middle of slide show play (step S1010: NO), asshown in FIG. 21, the information terminal acquires a battery voltagewhich is a voltage of the battery 20 (step S1100). Namely, the voltageof the battery 20 detected by the voltage detecting circuit 40 isacquired as digital data via the AD converter 30.

Then, the information terminal acquires a battery temperature which is atemperature of the battery 20 (step S1110). Namely, the batterytemperature as analog data detected by the temperature detecting circuit42 provided in the battery 20 is acquired as digital data via the ADconverter 30.

Thereafter, the information terminal acquires a constant load (stepS1120). This constant load changes according to the operation mode ofthe CPU 10. In this embodiment, it is assumed that the CPU 10 has threeoperation modes: low-speed, medium-speed, and high-speed operationmodes. The CPU 10 keeps track of in which mode out of these threeoperation modes the CPU 10 is at the moment. In this embodiment, theconstant load is 400 mA in the low-speed mode, the constant load is 500mA in the medium-speed mode, and the constant load is 600 mA in thehigh-speed mode.

Subsequently, the information terminal acquires a hard disk driveoperating rate (step S1130). In this embodiment, based on the accesssignal outputted from the hard disk drive 14, the CPU 10 can calculate aratio between a period of time when the hard disk drive 14 is accessedand a period of time when it is not accessed at any time. In thisembodiment, this access period ratio is defined as the hard disk driveoperating rate.

Then, the information terminal acquires an LCD backlight luminancecoefficient (step S1140). In this embodiment, the CPU 10 outputs aluminance signal which controls the luminance of the LCD backlight 12 tothe LCD backlight 12. Hence, the CPU 10 can keep track of a luminancecoefficient of the LCD backlight 12 based on this luminance. In thisembodiment, the LCD backlight luminance coefficient can be set between0% and 100% in steps of 10%.

Thereafter, the information terminal calculates a load (step S1150). Inthis embodiment, the load is found by the following expression (7).load=constant load+hard disk drive access load×hard disk drive operatingrate+LCD load×LCD backlight luminance coefficient   (7)

In this embodiment, it is assumed that the hard disk drive access loadis, for example, 500 mA, and the LCD load is, for example, 100 mA. Bysubstituting the constant load acquired in step S1120, the hard diskdrive operating rate acquired in step S1130, and the LCD backlightluminance coefficient acquired in step S1140 into this expression, acurrent load can be calculated.

Subsequently, a voltage-remaining capacity conversion table whichcorresponds to the battery temperature is generated (step S1160). Inthis embodiment, four kinds of voltage-remaining capacity conversiontables according to temperature are stored in the ROM 34 in the CPU 10.The structures of the voltage-remaining capacity conversion tablesstored in the ROM 34 in this embodiment are the same as those in FIG. 4to FIG. 7 in the aforementioned first embodiment.

As can be seen from these figures, in this embodiment, the relationbetween the remaining capacity and the battery voltage is tabulated withthree loads of 400 mA, 800 mA, and 1200 mA as representative values.Using these voltage-remaining capacity conversion tables, avoltage-remaining capacity conversion table at the battery temperatureacquired in step S1110 is generated by line interpolation.

For example, it is assumed that the battery temperature acquired in stepS1110 is 20° C. In this case, by linearly interpolating voltage valuesin the 15° C. voltage-remaining capacity conversion table TB20 shown inFIG. 5 and voltage values in the 25° C. voltage-remaining capacityconversion table TB30 shown in FIG. 6, voltage values in the 20° C.voltage-remaining capacity conversion table TB 50 are generated. Morespecifically, a voltage Y after correction can be calculated by thefollowing expression (8) $\begin{matrix}{Y = {{{\frac{\left( {{Y\quad 2} - {Y\quad 1}} \right)}{\left( {{T\quad 2} - {T\quad 1}} \right)}\left( {T - {T\quad 1}} \right)} + {Y\quad 1\quad{where}\quad T\quad 1}} < {T\quad 2}}} & (8)\end{matrix}$where T1 (15° C.) is the temperature of the low-temperature sidevoltage-remaining capacity conversion table, T2 (25° C.) is thetemperature of the high-temperature side voltage-remaining capacityconversion table, T (20° C.) is the battery temperature, Y1 is a voltagevalue at T1, and Y2 is a voltage value at T2.

Consequently, the voltage-remaining capacity conversion table TB50 whenthe calculated battery temperature is 20° C. is as shown in FIG. 8. Thisvoltage-remaining capacity conversion table TB50 is stored in the RAM 32of the CPU 10.

Incidentally, in this embodiment, by using the 5° C. and 15° C.voltage-remaining capacity conversion tables when the batterytemperature is lower than 5° C. and using the 25° C. and 45° C.voltage-remaining capacity conversion tables when the batterytemperature is higher than 45° C., and substituting corresponding valuesinto the expression (8), voltage-remaining capacity conversion tables atthese temperatures can be obtained.

Then, as shown in FIG. 21, the information terminal generates avoltage-remaining capacity conversion table corresponding to the loadcalculated in step S1150 (step S1170). Namely, based on thevoltage-remaining capacity conversion table generated in step S1160, thevoltage-remaining capacity conversion table corresponding to the loadcalculated in step S1150 is generated and stored in the RAM 32.

For example, it is assumed that the load calculated in step S1150 is1000 mA. In this case, by linearly interpolating voltage values at 800mA and voltage values at 1200 mA in the voltage-remaining capacityconversion table TB50 shown in FIG. 8, voltage values in thevoltage-remaining capacity conversion table TB60 at 1000 mA aregenerated. More specifically, a voltage Y after correction can becalculated by the following expression (9) $\begin{matrix}{Y = {{{\frac{\left( {{Y\quad 2} - {Y\quad 1}} \right)}{\left( {{L\quad 2} - {L\quad 1}} \right)}\left( {L - {L\quad 1}} \right)} + {Y\quad 1\quad{where}\quad L\quad 1}} < {L\quad 2}}} & (9)\end{matrix}$where L1 (800 mA) is a low-load side current value, L2 (1200 mA) is ahigh-load side current value, L is the load calculated in step S1150, Y1is a voltage value at L1, and Y2 is a voltage value at L2.

Consequently, the voltage-remaining capacity conversion table TB60 whenthe calculated load is 1000 mA is as shown in FIG. 9.

Thereafter, as shown in FIG. 21, the information terminal calculates abattery remaining capacity based on the voltage-remaining capacityconversion table TB60 after the load is corrected and the temperature iscorrected (step S1180). Namely, by linearly interpolating numericalvalues in the voltage-remaining capacity conversion table TB60 stored inthe RAM 32, a battery remaining capacity corresponding to the batteryvoltage acquired in step S1100 is calculated.

For example, it is assumed that the battery voltage acquired in stepS1100 is 3.55 V In this case, by linearly interpolating 3.54 V (batteryremaining capacity of 40%) and 3.60 V (battery remaining capacity of50%) in the voltage-remaining capacity conversion table TB60 shown inFIG. 9, the battery remaining capacity when the battery voltage is 3.55V is calculated. More specifically, a battery remaining capacity X aftercorrection can be calculated by the following expression (10)$\begin{matrix}{Y = {{{\frac{\left( {{X\quad 2} - {X\quad 1}} \right)}{\left( {{Y\quad 2} - {Y\quad 1}} \right)}\left( {Y - {Y\quad 1}} \right)} + {X\quad 1\quad{where}\quad Y\quad 1}} < {Y\quad 2}}} & (10)\end{matrix}$where Y1 (3.54 V) is a low-voltage side voltage value, Y2 (3.60 V) is ahigh-voltage side voltage value, Y is the voltage acquired in stepS1100, X1 is a battery remaining capacity at Y1, and X2 is a batteryremaining capacity at Y2.

Consequently, the result of calculation of the battery remainingcapacity is approximately 42%. In this embodiment, this calculatedbattery remaining capacity is temporarily stored in the RAM 32.

Thereafter, as shown in FIG. 21, the information terminal reads thecalculated battery remaining capacity from the RAM 32 and displays it onthe display 18 (step S1190). Various methods of displaying the batteryremaining capacity are thought out. For example, with a screen of theinformation terminal as the display 18, 42% may be displayednumerically, or with a bar-form liquid crystal display as the display18, a bar of this liquid crystal display may have a length correspondingto 42%.

As described above, according to this embodiment, the operating rate ofa unit (for example, the hard disk drive 14, the LCD backlight 12, theoperation mode of the CPU 10, or the like) which greatly contributes toload change is calculated by measuring a signal which the unit outputsor a signal which the unit receives, and by making a correction based onthe calculated result, the battery remaining capacity is displayed withhigh precision. Moreover, the correction is made using the CPU 10 whichis originally built in the information terminal, whereby the addition ofa new unit is not necessary, which can realize size reduction and costreduction of the information terminal.

Further, the battery temperature of the battery 20 is detected using thetemperature detecting circuit 42 and the correction is further madebased on this battery temperature, whereby the battery remainingcapacity can be displayed with higher precision.

Furthermore, when the information terminal is performing such processingthat the hard disk drive 14 is accessed at certain time intervals, theprocessing of calculating the battery remaining capacity is notperformed while the hard disk drive 14 is being accessed. After theaccess to the hard disk drive 14 is completed, the processing ofcalculating the battery remaining capacity is performed, so that thebattery remaining capacity can be calculated excluding a period when,due to the access to the hard disk drive 14, the load increases in ashort time and thereby the voltage of the battery 20 drops sharply.Consequently, the battery remaining capacity can be calculated withhigher precision.

Fourth Embodiment

In the aforementioned third embodiment, the hard disk drive operatingrate is calculated based on the access signal of the hard disk drive 14to calculate the load of the hard disk drive 14, but in the fourthembodiment, as in the aforementioned second embodiment, the state of thehard disk drive 14 is specified more precisely, and thereby the load ofthe hard disk drive 14 is found more precisely.

Incidentally, it is assumed that the hard disk drive 14 according tothis embodiment has five operating states such as shown in FIG. 10 andFIG. 11 as in the aforementioned second embodiment. It is also assumedthat the internal configuration of the information terminal is the sameas that in FIG. 14 in the aforementioned second embodiment.

Next, hard disk drive load count processing in this embodiment will beexplained. FIG. 22 is a flowchart explaining the contents of the harddisk drive load count processing according to this embodiment. The harddisk drive load count processing shown in FIG. 22 is realized by makingthe CPU 10 read and execute a hard disk drive load count processingprogram stored in the ROM 34. This hard disk drive load count processingis started every 31.25 ms to make a count as described above.

The processing from step S100 to step S116 of the hard disk drive loadcount processing in FIG. 22 is the same as that in the aforementionedsecond embodiment.

After these step S102, step S106, step S110, step S114, and step S116,the information terminal judges whether one second or more has passedsince the load of the hard disk drive 14 was calculated last time (stepS2000). When one second or more has not passed (step S2000: NO), thishard disk drive load count processing is ended.

On the other hand, when one second or more has passed since the load ofthe hard disk drive 14 was calculated (step S2000: YES), the hard diskdrive load is calculated (step S2010). In this embodiment, the load ofthe hard disk drive 14 is calculated based on the aforementionedexpression (5). Namely, the load of the hard disk drive 14 is calculatedbased on values of respective counters as a result of samplings of thestate of the hard disk drive 14 during the immediately preceding onesecond. More specifically, by substituting the count number of N_ON, thecount number of N_OFF PI, the count number of N_OFF_AI, the count numberof N_OFF_LPI, and the count number of N_OFF_ST into the expression (5),the current load of the hard disk drive 14 can be calculated.

Then, the information terminal clears these counters N_ON, N_OFF_PI,N_OFF_AI, N_OFF_LPI, and N_OFF_ST and sets them to zero (step S2020).Then, this hard disk drive load count processing is ended.

Next, battery remaining capacity calculation processing in thisembodiment will be explained. FIG. 23 is a part of a flowchartexplaining the contents of the battery remaining capacity calculationprocessing according to this embodiment and shows processing subsequentto FIG. 20 in the third embodiment. This battery remaining capacitycalculation processing shown in FIG. 23 is realized by making the CPU 10read and execute a battery remaining capacity calculation processingprogram stored in the ROM 34. In this embodiment, this battery remainingcapacity calculation processing is started once per second.

As shown in FIG. 23, when the information terminal is neither in themiddle of moving image reproduction, in the middle of soundreproduction, nor in the middle of slide show play (step S1010: NO) orone second or more has passed since the access to the hard disk drive iscompleted (step S1050: Yes) in FIG. 20, the information terminalacquires a battery voltage which is a voltage of the battery 20 (stepS1100). Namely, the voltage of the battery 20 detected by the voltagedetecting circuit 40 is acquired as digital data via the AD converter30.

Then, the information terminal acquires a battery temperature which is atemperature of the battery 20 (step S1110). Namely, the batterytemperature as analog data detected by the temperature detecting circuit42 provided in the battery 20 is acquired as digital data via the ADconverter 30.

Thereafter, the information terminal acquires a constant load (stepS1120). This constant load changes according to the operation mode ofthe CPU 10. In this embodiment, it is assumed that the CPU 10 has threeoperation modes: low-speed, medium-speed, and high-speed operationmodes. The CPU 10 keeps track of in which mode out of these threeoperation modes the CPU 10 is at the moment. In this embodiment, theconstant load is 400 mA in the low-speed mode, the constant load is 500mA in the medium-speed mode, and the constant load is 600 mA at thehigh-speed mode.

Subsequently, the information terminal acquires a load of the hard diskdrive 14 (step S2100). More specifically, the information terminalacquires the load of the hard disk drive 14 calculated by theaforementioned hard disk drive load count processing.

Then, the information terminal acquires an LCD backlight luminancecoefficient (step S1140). In this embodiment, the CPU 10 outputs aluminance signal which controls the luminance of the LCD backlight 12 tothe LCD backlight 12. Hence, the CPU 10 can keep track of a luminancecoefficient of the LCD backlight 12 based on this luminance. In thisembodiment, the LCD backlight luminance coefficient can be set between0% and 100% in steps of 10%.

Thereafter, the information terminal calculates a whole load (stepS1150). In this embodiment, the whole load is calculated based on theaforementioned expression (6). The processing after this is the same asthat in the aforementioned third embodiment, and hence the explanationthereof is omitted. Moreover, the voltage-remaining capacity conversiontables TB10 to TB40 according to temperature included in the informationterminal according to this embodiment are the same as those in FIG. 4 toFIG. 7 in the aforementioned third embodiment, and hence the explanationthereof is omitted.

As described above, according to this embodiment, the load of the harddisk drive 14 is calculated with higher precision based on the operatingstates of the hard disk drive 14. Consequently, the battery remainingcapacity can be displayed with higher precision.

Moreover, when the information terminal is performing such processingthat the hard disk drive 14 is accessed at certain time intervals, theprocessing of calculating the battery remaining capacity is notperformed while the hard disk drive 14 is being accessed. After theaccess to the hard disk drive 14 is completed, the processing ofcalculating the battery remaining capacity is performed, so that thebattery remaining capacity can be calculated excluding a period when,due to the access to the hard disk drive 14, the load increases in ashort time and thereby the voltage of the battery 20 drops sharply.Consequently, the battery remaining capacity can be calculated withhigher precision.

Fifth Embodiment

The fifth embodiment is a modification of the aforementioned thirdembodiment. The hard disk drive operating rate which is the load of thehard disk drive 14 is monitored, and the battery remaining capacity iscalculated when the hard disk drive operating rate is lower than a givenvalue, but the battery remaining capacity is not calculated when it isequal to or higher than the given value. This makes it possible to avoidcalculating the battery remaining capacity with a large error when theload of the hard disk drive 14 temporarily increases. Only pointsdifferent from the aforementioned third embodiment will be describedbelow.

FIG. 24 is a flowchart explaining the contents of battery remainingcapacity calculation processing according to this embodiment. Thisbattery remaining capacity calculation processing shown in FIG. 24 isrealized by making the CPU 10 read and execute a battery remainingcapacity calculation processing program stored in the ROM 34. In thisembodiment, this battery remaining capacity calculation processing isexecuted regularly at certain time intervals.

As shown in FIG. 24, first, the information terminal acquires a harddisk drive operating rate (step S3000). This hard disk drive operatingrate is a numeric value obtained by the CPU 10 calculating a ratiobetween a period of time when the hard disk drive 14 is accessed and aperiod of time when it is not accessed based on the access signaloutputted from the hard disk drive 14 as in the aforementioned thirdembodiment.

Then, the information terminal judges whether the hard disk driveoperating rate is lower than a given value (step S3010). In thisembodiment, for example, whether the hard disk drive operating rate islower than 0.1 is judged. Here, the idea that the hard disk driveoperating rate is lower than 0.1 means that, for example, when theperiod of time when the hard disk drive 14 is accessed during theimmediately preceding one second is defined as 1, the period of timewhen the hard disk drive 14 is not accessed is larger than 10.

When the hard disk drive operating rate is not lower than 0.1 (stepS3010: NO), the processing returns to step S3000. Namely, the subsequentprocessing for calculating the battery remaining capacity is notperformed.

On the other hand, when the hard disk drive operating rate is lower than0.1 (step S3010: YES), as in the aforementioned third embodiment, theprocessing from step S1100 to step S1190 is performed. Note that thehard disk drive operating rate is acquired in step S3000, so that stepS1130 can be omitted.

As described above, according to the information terminal of thisembodiment, when the load of the hard disk drive 14 is lower than thegiven value, the processing of calculating the battery remainingcapacity is performed, but when the load is equal to or higher than thegiven value, the processing of calculating the battery remainingcapacity is not performed. Consequently, the battery remaining capacitycan be calculated excluding a period when, due to the access to the harddisk drive 14, the load increases in a short time and thereby thevoltage of the battery 20 drops sharply. Consequently, the batteryremaining capacity can be calculated with higher precision.

Sixth Embodiment

The sixth embodiment is a modification of the aforementioned fourthembodiment. The hard disk drive load is monitored, and the batteryremaining capacity is calculated when the hard disk drive load is lowerthan a given value, but the battery remaining capacity is not calculatedwhen it is equal to or higher than the given value. This makes itpossible to avoid calculating the battery remaining capacity with alarge error when the load of the hard disk drive 14 temporarilyincreases. Only points different from the aforementioned fourthembodiment will be described below.

FIG. 25 is a flowchart explaining the contents of battery remainingcapacity calculation processing according to this embodiment. Thisbattery remaining capacity calculation processing shown in FIG. 25 isrealized by making the CPU 10 read and execute a battery remainingcapacity calculation processing program stored in the ROM 34. In thisembodiment, this battery remaining capacity calculation processing isexecuted regularly at certain time intervals.

As shown in FIG. 25, first, the information terminal acquires a load ofthe hard disk drive 14 (step S4000). This load of the hard disk drive 14is a numeric value calculated by the hard disk drive load countprocessing explained in the aforementioned fourth embodiment.

Then, the information terminal judges whether load of the hard diskdrive 14 is lower than a given value (step S4010). In this embodiment,for example, whether the load of the hard disk drive 14 is lower than200 mA is judged. Here, the idea that the load of the hard disk drive 14is lower than 200 mA means that in the aforementioned example,approximately one or more second has passed since the hard disk drive 14was brought into the active idle state where the current consumption is190 mA.

When the load of the hard disk drive 14 is not lower than 200 mA (stepS4010: NO), the processing returns to step S4000. Namely, the subsequentprocessing for calculating the battery remaining capacity is notperformed.

On the other hand, when the load of the hard disk drive 14 is lower than200 mA (step 4010: YES), as in the aforementioned fourth embodiment, theprocessing from step S1100 to step S1190 is performed. Note that theload of the hard disk drive 14 is acquired in step S4000, so that stepS2100 can be omitted.

As described above, according to the information terminal of thisembodiment, when the load of the hard disk drive 14 is lower than thegiven value, the processing of calculating the battery remainingcapacity is performed, but when the load is equal to or higher than thegiven value, the processing of calculating the battery remainingcapacity is not performed. Consequently, the battery remaining capacitycan be calculated excluding a period when, due to the access to the harddisk drive 14, the load increases in a short time and thereby thevoltage of the battery 20 drops sharply. Consequently, the batteryremaining capacity can be calculated with higher precision.

It should be mentioned that the present invention is not limited to theaforementioned embodiments, and various changes may be made therein. Forexample, in the aforementioned embodiments, the battery remainingcapacity is displayed as it is, but it may be converted into a remainingavailable time and then displayed. Namely, what users really want toknow is information on how much more time the information terminal canbe used under the same use as at present. In the aforementionedembodiments, load change can be estimated even in the informationterminal with large load change, and therefore the remaining availabletime can be calculated based on the value of the load and the batteryremaining capacity. It is needless to say that it may be displayed inreal time. Hence, for example, when the user is browsing moving images,the user can precisely know how much more time the user can browse them,or when the user is backing up data, the user can precisely know howmuch more time the user can transfer data.

Moreover, in the aforementioned embodiments, the LCD backlight 12, thehard disk drive 14, and the CPU load are shown as examples of elementsof a drive with large load change, but elements of the drive other thanthese may be added. Alternatively, out of these elements of the drive,some elements can be omitted. For example, the LCD backlight 12 does notexert much influence on load change, so that it may be left out ofaccount when the load is calculated. Alternatively, the load may becalculated with these elements of the drive being set to a fixedconstant. For example, the load may be calculated with the LCD backlight12 being set to a fixed value of 100 mA irrespective of its luminancecoefficient. Further, the hard disk drive 14 is an example of a datastorage which stores data, and other kinds of data storages such as aflexible disk and a DVD are also available as long as they store datawhich the information terminal accesses.

Further, the current consumptions and periods of time when therespective states of the hard disk drive 14 are maintained used in theaforementioned embodiments are shown only as examples, and they changeaccording to the model number of the hard disk drive 14 and firmwarewhich controls it.

Furthermore, in the aforementioned third embodiment and fourthembodiment, only when the information terminal is performing the processof accessing the hard disk drive 14 at certain time intervals, thebattery remaining capacity is calculated after the access to the harddisk drive 14 is completed, but even when the information terminal isnot performing the processing of accessing the hard disk drive 14 at thecertain time intervals, the battery remaining capacity may be calculatedafter the access to the hard disk drive 14 is completed.

Contrary to this, in the aforementioned fifth embodiment and sixthembodiment, only when the load of the hard disk drive 14 is lower thanthe given value irrespective of processing executed by the informationterminal, the battery remaining capacity is calculated, but as in theaforementioned third embodiment and fourth embodiment, it is alsopossible that only when the information terminal is performing theprocessing of accessing the hard disk drive 14 at the certain timeintervals, the battery remaining capacity is calculated when the load ofthe hard disk drive 14 is lower than the given value, and the batteryremaining capacity is not calculated when the load thereof is equal toor higher than the given value.

Moreover, in the aforementioned embodiments, the processing ofcalculating the battery remaining capacity is not performed when thehard disk drive 14 is being accessed, but during this time, the displayof the battery remaining capacity until this time may be continued as itis or the display of the battery remaining capacity may not beperformed.

Further, in the aforementioned embodiments, the constant load isdetermined based on the operation mode of the CPU 10, but the constantload may be changed according to the operation mode of the informationterminal. For example, as shown in FIG. 18, it is also possible toassume that the constant load is 200 mA when USB data transfer isperformed as the processing contents executed by the informationterminal, the constant load is 400 mA when still image reproduction isperformed, and that the constant load is 450 mA when moving imagereproduction is performed. This judgment needs to be performed in stepS14 described above. Consequently, when the information terminalperforms plural kinds of processing contents, the constant load can beobtained simply with high precision.

As concerns each processing explained in the aforementioned embodiments,it is possible to record a program to execute each processing on arecording medium such as a flexible disk, a CD-ROM (Compact Disc-ReadOnly Memory), a ROM, a memory card, or the like and distribute thisprogram in the form of the recording medium. In this case, theaforementioned embodiments can be realized by making the informationterminal read the recording medium on which this program is recorded andexecute this program.

Furthermore, the information terminal sometimes has other programs suchas an operating system, other application programs, and the like. Inthis case, by using these other programs in the information terminal, acommand, which calls a program to realize processing equal to that inthe aforementioned embodiments out of programs in the informationterminal, may be recorded on the recording medium.

Moreover, such a program can be distributed not in the form of therecording medium but in the form of a carrier wave via a network. Theprogram transmitted in the form of the carrier wave over the network isincorporated in the information terminal, and the aforementionedembodiments can be realized by executing this program.

Further, when being recorded on the recording medium or transmitted asthe carrier wave over the network, the program is sometimes encrypted orcompressed. In this case, the information terminal which has read theprogram from the recording medium or the carrier wave needs to executethe program after decrypting or expanding the program.

Furthermore, the processing according to the aforementioned firstembodiment and second embodiment can be realized by hardware as shown inFIG. 26. In FIG. 26, a controller 100 is composed of hardware such as anASIC. In the example in FIG. 26, the controller 100 includes a loadcalculator 102, a battery remaining capacity calculator 104, and aremaining available time calculator 106.

The load calculator 102 calculates the load on the battery 20 in thisinformation terminal. The battery remaining capacity calculator 104calculates the battery remaining capacity based on the battery voltage,and at this time, calculates the battery remaining capacity correctedbased on the load calculated by the load calculator 102.

Moreover, the load calculator 102 calculates the hard disk driveoperating rate based on the ratio between a period of time when the harddisk drive 14 is accessed and a period of time when it is not accessed,and finds the load of the hard disk drive 14 based on the hard diskdrive operating rate.

Further, when the hard disk drive 14 has plural states different incurrent consumption according to its operating state even if the harddisk drive 14 is not accessed, the load calculator 102 finds the load ofthe hard disk drive 14 based on a period of time when the hard diskdrive 14 is accessed and periods of time in respective operating stateswhen the hard disk drive is not accessed.

Furthermore, the load calculator acquires the operation mode of the CPU10, and finds a load of the CPU 10 based on this operation mode.Besides, the load calculator 102 finds the load on the battery 20 basedon processing contents processed by the information terminal.

Moreover, the load calculator 102 acquires the luminance of the LCDbacklight 12, calculates the LCD backlight luminance coefficient of theLCD backlight 12 based on this luminance, and finds the load of the LCDbacklight based on the LCD backlight luminance coefficient. Further, thebattery remaining capacity calculator 104 acquires the batterytemperature which is the temperature of the battery 20 and calculatesthe battery remaining capacity corrected based on the batterytemperature when the battery remaining capacity is calculated.

Concrete contents of processing in which the load calculator 102calculates the load and concrete contents of processing in which thebattery remaining capacity calculator 104 calculates the batteryremaining capacity are the same as the aforementioned processingcontents in FIG. 3 and FIG. 16.

A display 18 displays the battery remaining capacity calculated by thebattery remaining capacity calculator 104. The remaining available timecalculator 106 calculates the remaining available time which indicateshow much more time the information terminal can be used based on thebattery remaining capacity calculated by the battery remaining capacitycalculator 104 and the load calculated by the load calculator 102.

Moreover, when the processing according to the aforementioned thirdembodiment to sixth embodiment is realized by hardware, in the examplein FIG. 26, the load calculator 102 calculates the load on the battery20 in the information terminal. The battery remaining capacitycalculator 104 calculates the battery remaining capacity based on thebattery voltage, and at this time calculates the battery remainingcapacity corrected based on the load calculated by the load calculator102.

More specifically, in the aforementioned third embodiment and fifthembodiment, the load calculator 102 calculates the hard disk driveoperating rate based on the radio between a period of time when the harddisk drive 14 is accessed and a period of time when it is not accessed,and finds the load of the hard disk drive 14 based on this hard diskdrive operating rate.

Further, in the fourth embodiment and the sixth embodiment, when thehard disk drive 14 has plural states different in current consumptionaccording to its operating state even if the hard disk drive 14 is notaccessed, the load calculator 102 finds the load of the hard disk drive14 based on a period of time when the hard disk drive 14 is accessed andperiods of time in respective operating states when the hard disk driveis not accessed.

Furthermore, the load calculator 102 acquires the operation mode of theCPU 10, and finds the load of the CPU 10 based on this operation mode.Besides, the load calculator 102 finds the load on the battery 20 basedon processing contents processed by the information terminal.

Moreover, the load calculator 102 acquires the luminance of the LCDbacklight 12, calculates the LCD backlight luminance coefficient of theLCD backlight 12 based on this luminance, and finds the load of the LCDbacklight based on the LCD backlight luminance coefficient.

Further, the battery remaining capacity calculator 104 acquires thebattery temperature which is the temperature of the battery 20 andcalculates the battery remaining capacity corrected based on the batterytemperature when the battery remaining capacity is calculated. It isnoted, however, that in the third embodiment and the fourth embodiment,when the information terminal is performing such processing that thehard disk drive 14 is accessed at certain time intervals, the batteryremaining capacity calculator 104 does not calculate the batteryremaining capacity until the access to the hard disk drive 14 iscompleted.

Furthermore, in the fifth embodiment and the sixth embodiment, when theload of the hard disk drive 14 calculated by the load calculator 100 islower than a given value, the battery remaining capacity calculator 104calculates the battery remaining capacity, but when the load is equal toor higher than the given value, it does not calculate the batteryremaining capacity.

Concrete contents of processing in which the load calculator 102calculates the load and concrete contents of processing in which thebattery remaining capacity calculator 104 calculates the batteryremaining capacity are the same as the aforementioned processingcontents in the third embodiment and the sixth embodiment.

Additionally, the display 18 displays the battery remaining capacitycalculated by the battery remaining capacity calculator 104. Theremaining available time calculator 106 calculates the remainingavailable time which indicates how much more time the informationterminal can be used based on the battery remaining capacity calculatedby the battery remaining capacity calculator 104 and the load calculatedby the load calculator 102.

1. An information terminal driven by a battery, comprising: a voltagedetector configured to detect a battery voltage which is a voltage ofthe battery; a drive unit configured to be driven upon receiving asupply of a power source from the battery; a load calculator configuredto calculate a load on the battery of the drive unit; and a batteryremaining capacity calculator configured to calculate a batteryremaining capacity based on the battery voltage, the battery remainingcapacity calculator calculating the battery remaining capacity correctedbased on the load calculated by the load calculator, wherein the driveunit includes a hard disk drive, and the hard disk drive has pluralstates different in current consumption according to its operating stateeven when the hard disk drive is not accessed, and wherein the loadcalculator finds a load of the hard disk drive based on a period of timewhen the hard disk drive is accessed and periods of time in therespective operating states when the hard disk drive is not accessed. 2.An information terminal driven by a battery, comprising: a data storageconfigured to be driven upon receiving a supply of a power source fromthe battery, data being stored in the data storage; a voltage detectorconfigured to detect a battery voltage which is a voltage of thebattery; a battery remaining capacity calculator configured to calculatea battery remaining capacity based on the battery voltage, the batteryremaining capacity calculator calculating the battery remaining capacityafter access to the data storage is completed.
 3. The informationterminal according to claim 2, further comprising a load calculatorconfigured to calculate a load on the battery of the data storage,wherein the battery remaining capacity calculator calculates the batteryremaining capacity corrected based on the load calculated by the loadcalculator.
 4. The information terminal according to claim 3, furthercomprising a drive unit other than the data storage, which is drivenupon receiving a supply of a power source from the battery, wherein theload calculator calculates loads on the battery of the drive unit andthe data storage.
 5. The information terminal according to claim 3,wherein the load calculator calculates an operating rate of the datastorage based on a ratio between a period of time when the data storageis accessed and a period of time when the data storage is not accessedand finds a load of the data storage based on the operating rate of thedata storage.
 6. The information terminal according to claim 3, whereinthe data storage has plural states different in current consumptionaccording to its operating state even when the data storage is notaccessed, and the load calculator finds a load of the data storage basedon a period of time when the data storage is accessed and periods oftime in the respective operating states when the data storage is notaccessed.
 7. The information terminal according to claim 4, wherein thedrive unit includes a central processing unit of the informationterminal, and the load calculator finds a load of the central processingunit based on an operation mode of the central processing unit.
 8. Theinformation terminal according to claim 4, wherein the load calculatorfinds the load on the battery based on processing contents processed bythe information terminal.
 9. The information terminal according to claim4, wherein the drive unit includes an LCD backlight, and the loadcalculator calculates an LCD backlight luminance coefficient of the LCDbacklight based on a luminance of the LCD backlight and finds a load ofthe LCD backlight based on the LCD backlight luminance coefficient. 10.The information terminal according to claim 2, further comprising atemperature detector configured to detect a battery temperature which isa temperature of the battery, wherein the battery remaining capacitycalculator calculates the battery remaining capacity corrected based onthe battery temperature detected by the temperature detector.
 11. Theinformation terminal according to claim 2, further comprising a displayunit configured to display the battery remaining capacity calculated bythe battery remaining capacity calculator.
 12. The information terminalaccording to claim 2, further comprising a remaining available timecalculator configured to calculate a remaining available time whichindicates how much more time the information terminal can be used basedon the battery remaining capacity calculated by the battery remainingcapacity calculator and the load calculated by the load calculator. 13.The information terminal according to claim 2, wherein when processingof accessing data stored in the data storage is performed at certaintime intervals, the battery remaining capacity calculator calculates thebattery remaining capacity after the access to the data storage iscompleted.
 14. The information terminal according to claim 2, whereinwhen processing of accessing data stored in the data storage isperformed at certain time intervals, the battery remaining capacitycalculator calculates the battery remaining capacity after a lapse of apredetermined period of time from the completion of the access to thedata storage.
 15. An information terminal driven by a battery,comprising: a data storage configured to be driven upon receiving asupply of a power source from the battery and store data; a data storageload calculator configured to calculate a load of the data storage; avoltage detector configured to detect a battery voltage which is avoltage of the battery; and a battery remaining capacity calculatorconfigured to calculate a battery remaining capacity based on thebattery voltage, the battery remaining capacity calculator calculatingthe battery remaining capacity when the load of the data storagecalculated by the data storage load calculator is lower than a givenvalue.
 16. A battery remaining capacity calculating method in aninformation terminal driven by a battery, comprising the steps of:judging whether access to a data storage is completed, the data storagebeing driven upon receiving a supply of a power source from the battery;and calculating a battery remaining capacity based on a battery voltagewhich is a voltage of the battery after the access to the data storageis completed.
 17. A battery remaining capacity calculating method in aninformation terminal driven by a battery, comprising the steps of:calculating a load of a data storage which is driven upon receiving asupply of a power source from the battery; and calculating a batteryremaining capacity based on a battery voltage which is a voltage of thebattery when the calculated load is lower than a given value.
 18. Arecording medium, having a program for causing an information terminaldriven by a battery to calculate a battery remaining capacity recordedthereon, wherein the program causes the information terminal to executeprocess comprising the steps of: judging whether access to a datastorage is completed, the data storage being driven upon receiving asupply of a power source from the battery; and calculating a batteryremaining capacity based on a battery voltage which is a voltage of thebattery after the access to the data storage is completed.
 19. Arecording medium, having a program for causing an information terminaldriven by a battery to calculate a battery remaining capacity recordedthereon, wherein the program causes the information terminal to executeprocess comprising the steps of: calculating a load of a data storagewhich is driven upon receiving a supply of a power source from thebattery; and calculating a battery remaining capacity based on a batteryvoltage which is a voltage of the battery when the calculated load islower than a given value.